In large scale multiple needle quilting machines, several layers of fabric web are brought together at a quilting station where they are sewn together by the stitching of patterns thereon. The patterns are formed by moving the composite multiple layered fabric web relative to a bank of stitching elements that include an array of needles above the fabric and a corresponding array of loopers or other cooperating stitching elements below. The relative motion of the fabric and the stitching elements is often carried out under the control of a programmable controller.
The programs of the controllers are varied in order to produce a variety of patterns to satisfy the requirements of the customers of the quilted fabrics. These customers are often the manufacturers of mattresses and other upholstered items. The customers' requirements are varied, and each may order from a quilt manufacturer a number of different patterns in small or moderate quantities, requiring the quilt manufacturer to frequently change the pattern program and possibly also the fabric material.
When quilts are stitched, a series of a panel-length sections of quilted patterns emerge from a downstream end of the quilting station of the quilting machine as part of a single continuous web. The series might include multiple copies of the same pattern sewn on the same material, a series of different patterns sewn on the same material, or a series of the same or different patterns sewn on different types of material spliced together to form the continuous web. To automate the production control of various types of panels or batches of panels, quilting machines, such as that disclosed in U.S. Pat. No. 5,154,130, have for several years included a programmed controller that is programmed to cause the movement of the fabric relative to the stitching elements to produce the various patterns. The controllers have also been programmed to change from pattern to pattern in accordance with a production schedule, and to signal the need to splice materials where called for by the order description.
Each of the panel length sections of quilted web that emerge from the quilting station must ultimately be cut from the web to form individual quilted panels. This has been achieved by placing a panel cutter in line with and downstream of the quilting station. The panel cutter includes a transverse knife or blade that is actuated to cut transversely across the quilted fabric to separate the individual panels from the web. The stitching of various panels of one or more patterns onto a web of one or more material types and the cutting of the discrete quilted panels from the web at the proper point along the web requires coordination of the panel cutter knife in severing the individual panels from the web, the positioning of the web at the quilting station so that quilting needle movement properly locates the patterns on the web, and properly identifies the location of the splices in the fabric. This coordination has been conventionally carried out primarily with manual monitoring by an operator and manual decision making.
The coordination of a panel cutting operation with a stitching operation and the splicing of material in a web that is being formed into a series of quilted patterns is complicated by the phenomenon referred to in the quilting industry as "shrinkage". Shrinkage of the fabric is a result of the stitching together of multiple layers of fabric that include the top and bottom layers with a filler layer in between. As the layers are stitched together, the material tends to gather, causing the fabric to shorten dimensionally in the longitudinal direction along the web. The longitudinal shrinkage is the primary complicating factor in coordinating the operations on the web.
The amount of shrinkage varies among different patterns, due to the different amounts and configurations of the stitching called for by the patterns. When the fabric is under tension in the quilting machine, which is normally the case in that the web is generally pulled through the machine by feed rolls upstream of a particular station, the longitudinal dimensions of the pattern are only slightly, but nonetheless materially, affected by the so called shrinkage. Once the tension is released, however, such as when the fabric is discharged from the machine or fed to the panel cutter, the shrinkage is manifested in a greater shortening of the fabric, often in the order of ten percent of the tensioned length. This greater shortening also may vary, even without a change in the patterns or the material, due to ambient factors such as humidity in the plant in which the quilt is being made.
The dimensions of the cut unstressed panels are the dimensions to which the quilting, splicing and feeding of the web must be coordinated, since these are the specified dimensions of the finished product. In order to produce a panel of a given length, a section of the web of a somewhat greater length must be quilted, and the position and dimensions of the quilted patterns on the web must be adjusted to accommodate for the shrinkage that will occur. In addition, due to the shrinkage, the rate of feed of web through the quilting station and through the panel cutter will differ. Further, the cumulative effects of the shrinkage must be taken into account in order to minimize waste when different materials must be spliced together, and to synchronize the cutter to cut the panels precisely between the patterns.
Thus far, no effective way to control the apparatus to account for shrinkage, absent excessive manual intervention by an operator, has been provided in the prior art. Further, since a majority of the shrinkage occurs beyond the last feed element at the panel cutter, the programmed controllers of the prior art, as discussed above, are inadequate to coordinate automated batch production control where a panel cutter is to be incorporated into a more fully automated system. Accordingly, there remains a need for a more effective method and apparatus for control of the various stages of a quilter/panel-cutter machine that is adequately responsive to the shrinkage of the fabric.